A measurement signal for detecting the parameters of technical devices is the preferred means in many areas of technology for analyzing parameters and controlling or regulating these parameters on the basis of this analysis. The measurement signals usually exist in electronic form, such as electric voltages, for example.
Motor vehicle technology is one area of technology in which measurement signals play an important role is. They are used there to detect the parameters of various components of the vehicle, such as the parameters of the drive motor, for example, or the clutch, or the transmission, and to analyze them, so that these parameters or components of the motor vehicle can be controlled or regulated. Here, the parameters can be periodic or non-periodic in nature. One example of non-periodic parameters in motor vehicle technology is the speed of the vehicle, while the rotational angle position of the input shaft of the motor vehicle transmission is one of the periodic parameters.
It is often the case that the measurement signal detects not only the parameter that is to be analyzed, but also other parameters that are associated with this parameter. In such cases, the measurement signal does not correspond to the pure useful signal that is necessary for the analysis of the parameter, but is rather combined with an interference signal. The interference signals in the measurement signals quite often reach a magnitude that complicates or distorts analysis of the parameter to such an extent that the control or regulation of the parameter based on the analysis is no longer adequately possible.
In one case, which occurs very often in vehicular technology, the cause of an interference signal occurs periodically, and the cycle of this cause is known. The interference signal is then periodic as well, and the cycle of the interference signal is usually described in terms of an interference signal frequency. If the cause of the interference signal is known, the interference signal cycle is usually known as well. One example of this is the natural drive train oscillation that occurs in drive trains with a known cycle. The oscillation causes an interference signal which overlays, with a known interference signal frequency, the measurement signal of the initial speed of the transmission of a motor vehicle.
This results in the necessity of developing methods and the appurtenant devices by means of which the interference signals can be removed from a measurement signal, in order to detect the useful signal.
Various methods and appurtenant devices for this purpose are known from the state of the art.
One type of widely used method uses filter algorithms that are based on high-pass filters, low-pass filters, band-pass filters, or band rejection filters. However, these filter algorithms display numerous disadvantages. Thus, depending on the filter frequency or the cut-off frequency used at any given time, a phase delay can occur, which can have an adverse effect on a parameter. In addition, the filter parameters must be chosen in such a way that they are optimally adjusted to a certain filter frequency. If the filter frequency changes, the filter parameters must also be changed, in order to main the optimum adjustment. This is often adjusted for by using of a plurality of filters with different filter frequencies, but this is very complicated in terms of construction. If characteristic curves with steep gradients are required for the filters, the filter order also increases, and therefore the number of filter parameters, which also increases software and/or construction complexity.
Another type of method that is also often used is based on integral transformations. The German utility model DE 20 2004 009 922 U1 illustrates a few relevant integral transformations from the class of wavelet transformation. Wavelet transformations are very complicated in computational terms and cannot normally be used to control or regulate parameters in real time due to the limited computing power of the control or regulating devices of motor vehicles.
Another type of practically applicable method is based on a different type of integral transformation, the Fourier transformation, which is also mentioned in the German utility model DE 20 2004 009 922 U1. The disadvantage of Fourier transformations is that they are usually done with reference to a plurality of frequencies. Here too, the computational complexity is often so great that no analysis of the measurement signal in real time, and therefore also no control or regulation of the parameters on which the measurement signal is based, can be done by the control or regulating device of motor vehicles.